Service providers provide ATM (Asynchronous Transfer Mode) service by using ATM communication infrastructure and provide frame relay service by using frame relay communication infrastructure. Setting up dedicated communication infrastructure for each service, however, will require enormous cost.
Under these circumstances, service providers adopt a method of providing ATM service on MPLS (Multi Protocol Label Switching) communication infrastructure by setting up ATM and frame relay pseudo wires on MPLS.
Expansion of this concept of pseudo wire to Ethernet (registered trademark) is VPLS (Virtual Private LAN (Local Area Network) Service). VPLS is a technique for providing L2 (Layer 2) service on MPLS.
Relay wire or the like for the wide area Ethernet (registered trademark) uses PWE3 (Pseudo Wire Emulation Edge to Edge) technique (see e.g. Patent Literature 1).
The PWE3 technique is a technique for emulating the Ethernet (registered trademark) on the MPLS network for transmission. MPLS is a technique for providing the IP (Internet Protocol) network with concept of a path by executing transfer based on a label attached to a packet in place of an IP address.
For setting up the above-described pseudo wire on MPLS, it is necessary to know a MAC (Media Access Control) address of a facing device. There exist ARP (Address Resolution Protocol) and the like as a method of knowing a MAC address of a facing device when including an L3 (layer 3).
When limiting to an L2 layer, however, there exists no method of automatically obtaining a MAC address inherent in a facing device. In a communication mode using only an L2 layer, every time a failure occurs, configuration is re-set using a MAC address inherent in a device to which a facing device belongs. Re-setting of configuration involves troublesome re-setting because of physical long distance of a facing device and such human mistakes as erroneous read of a MAC address inherent in a device and as erroneous input at the time of configuration setting.
Patent Literature 1: Japanese Patent Laying-Open No. 2006-229985.
For setting up the above-described pseudo wire, there exists no method of automatically obtaining a MAC address inherent in a facing device when limiting to an L2 layer. Therefore, configuration using an inherent MAC address should be set by initial setting at both devices facing to each other, so that the configuration setting needs to be executed for the facing devices every time a MAC address inherent in a device used changes.
Thus, it is possible that pseudo wire configuration setting might not be executed with ease because it should be executed every time a MAC address inherent in a device changes and because a setting destination is a facing device at the time of setting up a pseudo wire to have a physically long distance. Further problem is a human error such as erroneous input at the time of setting configuration because an inherent MAC address which is unique cannot be determined unless the device itself is referred to.
Under these circumstances, an object of the present invention is to solve the above-described problems and provide a communication system, a network apparatus, a communication recovery method for use therein, and a program thereof which enable communication with a facing side to be recovered only by changing a data base of a switch on a transmission side.